<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python documentation Index' />
<link rel="first" href="lib.html" title='Python library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="optparse-standard-option-types.html" />
<link rel="prev" href="optparse-standard-option-actions.html" />
<link rel="parent" href="optparse-reference-guide.html" />
<link rel="next" href="optparse-standard-option-types.html" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name='aesop' content='information' />
<title>14.3.3.5 Option attributes</title>
</head>
<body>
<div class="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="14.3.3.4 standard option actions"
  href="optparse-standard-option-actions.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="14.3.3 reference Guide"
  href="optparse-reference-guide.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="14.3.3.6 standard option types"
  href="optparse-standard-option-types.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="optparse-standard-option-actions.html">14.3.3.4 Standard option actions</a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="optparse-reference-guide.html">14.3.3 Reference Guide</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="optparse-standard-option-types.html">14.3.3.6 Standard option types</a>
</div>
<hr /></div>
</div>
<!--End of Navigation Panel-->

<h3><a name="SECTION0016335000000000000000"></a><a name="optparse-option-attributes"></a>
<br>
14.3.3.5 Option attributes
</h3>

<p>
The following option attributes may be passed as keyword arguments
to <code>parser.add_option()</code>.  If you pass an option attribute
that is not relevant to a particular option, or fail to pass a required
option attribute, <tt class="module">optparse</tt> raises OptionError.

<ul>
<li> 
<tt class="member">action</tt> (default: <code>"store"</code>)

<p>
Determines <tt class="module">optparse</tt>'s behaviour when this option is seen on the command
line; the available options are documented above.

<p>
</li>
<li> 
<tt class="member">type</tt> (default: <code>"string"</code>)

<p>
The argument type expected by this option (e.g., <code>"string"</code> or
<code>"int"</code>); the available option types are documented below.

<p>
</li>
<li> 
<tt class="member">dest</tt> (default: derived from option strings)

<p>
If the option's action implies writing or modifying a value somewhere,
this tells <tt class="module">optparse</tt> where to write it: <tt class="member">dest</tt> names an attribute of the
<code>options</code> object that <tt class="module">optparse</tt> builds as it parses the command line.

<p>
</li>
<li> 
<code>default</code> (deprecated)

<p>
The value to use for this option's destination if the option is not
seen on the command line.  Deprecated; use <code>parser.set_defaults()</code>
instead.

<p>
</li>
<li> 
<code>nargs</code> (default: 1)

<p>
How many arguments of type <tt class="member">type</tt> should be consumed when this
option is seen.  If &gt; 1, <tt class="module">optparse</tt> will store a tuple of values to
<tt class="member">dest</tt>.

<p>
</li>
<li> 
<code>const</code>

<p>
For actions that store a constant value, the constant value to store.

<p>
</li>
<li> 
<code>choices</code>

<p>
For options of type <code>"choice"</code>, the list of strings the user
may choose from.

<p>
</li>
<li> 
<code>callback</code>

<p>
For options with action <code>"callback"</code>, the callable to call when this
option is seen.  See section&nbsp;<a href="optparse-option-callbacks.html#optparse-option-callbacks">14.3.4</a>, Option Callbacks for detail on the arguments
passed to <code>callable</code>.

<p>
</li>
<li> 
<code>callback_args</code>, <code>callback_kwargs</code>

<p>
Additional positional and keyword arguments to pass to <code>callback</code>
after the four standard callback arguments.

<p>
</li>
<li> 
<tt class="member">help</tt>

<p>
Help text to print for this option when listing all available options
after the user supplies a <tt class="member">help</tt> option (such as <code>"-help"</code>).
If no help text is supplied, the option will be listed without help
text.  To hide this option, use the special value <code>SUPPRESS_HELP</code>.

<p>
</li>
<li> 
<code>metavar</code> (default: derived from option strings)

<p>
Stand-in for the option argument(s) to use when printing help text.
See section&nbsp;<a href="optparse-tutorial.html#optparse-tutorial">14.3.2</a>, the tutorial for an example.

<p>
</li>
</ul>

<p>

<div class="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="14.3.3.4 standard option actions"
  href="optparse-standard-option-actions.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="14.3.3 reference Guide"
  href="optparse-reference-guide.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="14.3.3.6 standard option types"
  href="optparse-standard-option-types.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="optparse-standard-option-actions.html">14.3.3.4 Standard option actions</a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="optparse-reference-guide.html">14.3.3 Reference Guide</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="optparse-standard-option-types.html">14.3.3.6 Standard option types</a>
</div>
</div>
<hr />
<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
</div>
<!--End of Navigation Panel-->
<address>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</address>
</body>
</html>
